1. Field of the Invention.
This invention relates generally to disc valves and particularly to a rotary actuated straight line disc valve with a hydraulic or mechanical actuator.
2. Prior Art.
Controlling the flow of fluids from high pressure fluid sources such as oil and gas wells requires specialty equipment. Pressures as high as 20,000 pounds per square inch is commonly found in the oil field and pressures as high as 50,000 pounds per square inch are occasionally encountered. Besides the high pressures involved, the fluid itself also presents special problems. Grit and other particulate matter is easily entrained in the high pressure fluid flow. Additionally, the flow itself can be unpredictable, often having slugs of liquid mixed with gas.
Generally, the prior art high pressure valves use a right angle configuration. That is, the fluid enters the valve housing through an inlet passageway and makes a right angle turn through a discharge outlet. The actuating means, whether plug type or disc type, is generally positioned at the corner of the right angle. The actuator itself is generally aligned with the discharge outlet. Because of the aforementioned characteristics of the fluid flowing through the valve, these prior art valves are particularly prone to wear at the site of the turn. One method used to buffer the force of the fluid is shown in U.S. Pat. No. 4,493,336. However, even with the aforementioned improvements, the actuator portion of the valves tend to be large, often accounting for the majority of the bulk of the valve. Another shortcoming of the prior art valve actuators are that they contain several mechanical linkages thereby introducing unwanted hysteresis in the control mechanism.
High pressure valves present special problems with regard to seals. In the prior art valves, seals are exposed to the fluid being regulated and are subject to stress from heat, high pressure, chemical attack and abrasion. Typically, the seals are made of polymers which are specially formulated to withstand extremes in operating conditions.